The adjustment of the endshake of a timepiece wheel set is a difficult operation, performed by highly qualified personnel, often by the elastic deformation of a structural element, bar or suchlike, or by driving out a jewel and then driving it back in again. Mechanisms rarely incorporate adjustment means, due to the very small ranges of adjustment required, of several micrometers or of several hundredths of a millimeter at most, which are impossible to obtain using conventional micrometric means, such as external-internal threads, because of the operating plays required, which are greater than the required adjustment ranges. Moreover, the space necessarily required for any adjustment mechanism is rarely compatible with that of the timepiece movement.
CH Patent Application No 339136A in the name of BUREAU TECHNIQUE ERARD, describes a timepiece bearing including a concentric arrangement of a member forming the bearing body and a central member carrying at least one jewel hole. The axial position of the central member can be adjusted by imparting a rotation thereon in relation to the bearing body.
CH Patent Application No 356090A in the name of SEITZ & CO describes a bearing with an axial stop member removably mounted in a bearing body including one of the projecting portions which cooperate with helical ramps comprised in a setting forming said axial stop member.
US Patent Application No 4192136A in the name of ROBINSON describes an axial adjustment mechanism in a timepiece, based on the cooperation of helical inclined sectors.
US Patent Application No 2010/188941A1 in the name of SEIKO (FUJIEDA HISASHI) describes a bearing structure, with an entirely axial adjustment configuration, supporting in rotation a front end portion of a wheel arbour in relation to a base body, including: a bearing, a bearing support body carrying the bearing and having a male screw portion on an outer peripheral surface of the wheel arbour, and an adjustment nut provided with a female screw portion in thread engagement with the male screw portion of the bearing support body, adjusted in its movement in the direction of extension of the wheel arbour by the base body, and adapted to adjust the position of the bearing with respect to the direction of extension of the arbour via the bearing support member.